This proposal, which is a competing continuation of MH 58144 "Developmental trajectories of early behavior problems," proposes a follow-up of young children during middle childhood to address specific gaps in current research. Specifically, the application is to follow 3 cohorts of high risk male and female toddlers (n = 425) who have been assessed in multiple contexts, using multiple measures, including biological and behavioral measures, across multiple levels of analysis from age 2 to age 5.5 or age 7. The focus of the study has been on the global construct of externalizing problems, defined as aggression, destructive behavior, inattention, hyperactivity, and defiance, and the different pathways associated with the display of this global set of problems in toddlerhood. In this follow-up, we will be examining the pathways of specific subtypes of behavior problems from ages 7 to 10. One focus of the proposed work concerns one specific mechanism (self-regulation) that affects the trajectories of early problems, as well as two specific moderators (parenting and peer relationships) that influence the likelihood that a child will remain on a stable or persistent negative pathway during middle childhood. A second focus of this work is on the more distal risk factors, including socioeconomic status, parent functioning, and neighborhood quality, that affect trajectories of problems behavior via their influence on the more proximal mechanisms. The proposed project is both significant and timely because, despite the clear importance of early identification of children with acting-out, aggressive behavior problems, few longitudinal studies have been conducted with both boys and girls younger than 3 or 4 years of age examining the early display of these types of behaviors, the multiple factors contributing to such behavior, the different types of problems that may emerge in early childhood, and the complex pathways to later psychosocial functioning.